The chemical and mineral industries use many processes to transform materials into other substances with desired properties for commercial marketing. Typical materials which require processing at high temperatures are those used for the making of catalysts such as Zeolites and alumino-silicates, Titanium Dioxide for pigments, ceramic compounds and rare earth minerals. Materials that are processed at lower temperatures for simple drying often use another process called ‘plug flow’ vibrating beds. Both are presented here as Prior Art.
1. Rotary Calciners—The traditional method of indirectly heating of granular solids is in rotary calciners. U.S. Pat. Nos. 1,995,948 and 2,026,441 disclose primary mechanisms of rotating a heated shell for this purpose. A rotary calciner shown in FIG. 1 is comprised of a cylindrical tube made of heat resistant alloy that is surrounded by a stationary furnace. Steel tires are fitted around the ends of the cylindrical tube which protrude from each end of the stationary furnace. The steel tires are supported by steel trunnion wheels. A ring gear surrounds one end of the cylindrical tube that is driven by a pinion gear which is mounted on a motor reducer causing the tube to slowly rotate.
The exterior of the cylindrical tube is indirectly heated by the furnace and granular material is fed in to the front of the cylindrical tube by a mechanical feeder. As the tube rotates, the granular material is tumbled in a circular cascading motion as shown in FIG. 2. As the granular material is heated, it slowly migrates to the end of the tube and discharges the cylindrical tube through a discharge breeching.
Key to the operation of the rotary calciner is the circular or ‘cascading’ motion of the granular material which continually exposes material to the radiant heat from the cylindrical tube heated by the furnace. Rotary calciners are also sloped slightly downward from the feed end to the discharge end to aid in the migration of the granular material from feed to discharge.
Typical operating temperatures of rotary calciners are between 800° F. and 2,000° F.
Common to all rotary calciners is the expensive mechanical hardware required only to rotate the shell. The steel tires are forged fabrications and require flame hardening to resist the high contact surface stresses. Also the steel trunnion rollers require flame or induction hardening. The large ring gears and pinion gears are custom made and expensive to manufacture. The cylindrical tube must be made of expensive heat resistant alloys. Supporting the cylindrical tube over the large span between the steel tires requires cylindrical tube to be very thick to withstand the stresses created having the cylindrical tube supported as a simple beam by the steel trunnion wheels outside the furnace.
The entire rotary calciner is usually sloped at a rise of ¼ inch to one foot to promote the migration of granular material from the feed to the discharge as the cylindrical tube is rotated.
2. Vibrating bed equipment—Other processes used by industry is for the transport, screening and thermal drying of granular material in vibrating beds. U.S. Pat. No. 3,922,430 disclose primary mechanisms of a motorized eccentric mass to induce vibration. As shown in FIG. 3 Prior Art, a vessel contains the granular material and is fed at one end through a feed chute. Attached to the vessel is a vibrator mount to which is attached two counter-rotating rotary vibrators. A rotary vibrator is comprised of a motor with eccentric weights fitted to each end of the motor. The entire device is mounted on vibration isolators which allow the vessel, vibrator mount, and rotary vibrators to freely vibrate while isolating the vibrations from the surroundings.
When two rotary vibrators are energized in opposite rotational direction of each other the inertial effect is to cause a counter rotation 180° of phase displacement of each other. This creates a linear path of vibration perpendicular to a line defined by the two centers of the rotary vibrators. The result is a repeated linear path of motion and force for each revolution as shown by arrow 21′ in FIG. 4 Prior Art. The force required of the rotary vibrators to create the motion is generally three to four times the weight of the vibrating mass.
The repeated linear force is transmitted through the vessel and causes the granular material to be transported in a linear path parallel to the long axis of the vessel referred to as ‘Plug Flow’ motion. Retaining the granular material within the vessel is a vessel dam. During operation, the granular material fills to the top of the vessel dam until the vibrating forces cause the granular material to leap over the top of the vessel dam and discharge from the discharge chute.
Typical operating temperatures of vibrating dryers are between 160° F. and 650° F. Typical vibrating vessels depicted by FIG. 3 such as screens, dryers and conveyors are quite common in processing granular solids. These vessels orient the vibrations in the direction of solids transport known as ‘Plug Flow’ since the orientation of the vibration is aligned in the direction of material movement.